include/linux/blk-cgroup.h

   1 #ifndef _BLK_CGROUP_H
   2 #define _BLK_CGROUP_H
   3 /*
   4  * Common Block IO controller cgroup interface
   5  *
   6  * Based on ideas and code from CFQ, CFS and BFQ:
   7  * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
   8  *
   9  * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
  10  *                    Paolo Valente <paolo.valente@unimore.it>
  11  *
  12  * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
  13  *                    Nauman Rafique <nauman@google.com>
  14  */
  15
  16 #include <linux/cgroup.h>
  17 #include <linux/u64_stats_sync.h>
  18 #include <linux/seq_file.h>
  19 #include <linux/radix-tree.h>
  20 #include <linux/blkdev.h>
  21 #include <linux/atomic.h>
  22
  23 /* Max limits for throttle policy */
  24 #define THROTL_IOPS_MAX         UINT_MAX
  25
  26 #ifdef CONFIG_BLK_CGROUP
  27
  28 enum blkg_rwstat_type {
  29         BLKG_RWSTAT_READ,
  30         BLKG_RWSTAT_WRITE,
  31         BLKG_RWSTAT_SYNC,
  32         BLKG_RWSTAT_ASYNC,
  33
  34         BLKG_RWSTAT_NR,
  35         BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
  36 };
  37
  38 struct blkcg_gq;
  39
  40 struct blkcg {
  41         struct cgroup_subsys_state      css;
  42         spinlock_t                      lock;
  43
  44         struct radix_tree_root          blkg_tree;
  45         struct blkcg_gq                 *blkg_hint;
  46         struct hlist_head               blkg_list;
  47
  48         struct blkcg_policy_data        *pd[BLKCG_MAX_POLS];
  49
  50         struct list_head                all_blkcgs_node;
  51 #ifdef CONFIG_CGROUP_WRITEBACK
  52         struct list_head                cgwb_list;
  53 #endif
  54 };
  55
  56 struct blkg_stat {
  57         struct u64_stats_sync           syncp;
  58         uint64_t                        cnt;
  59 };
  60
  61 struct blkg_rwstat {
  62         struct u64_stats_sync           syncp;
  63         uint64_t                        cnt[BLKG_RWSTAT_NR];
  64 };
  65
  66 /*
  67  * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
  68  * request_queue (q).  This is used by blkcg policies which need to track
  69  * information per blkcg - q pair.
  70  *
  71  * There can be multiple active blkcg policies and each has its private
  72  * data on each blkg, the size of which is determined by
  73  * blkcg_policy->pd_size.  blkcg core allocates and frees such areas
  74  * together with blkg and invokes pd_init/exit_fn() methods.
  75  *
  76  * Such private data must embed struct blkg_policy_data (pd) at the
  77  * beginning and pd_size can't be smaller than pd.
  78  */
  79 struct blkg_policy_data {
  80         /* the blkg and policy id this per-policy data belongs to */
  81         struct blkcg_gq                 *blkg;
  82         int                             plid;
  83
  84         /* used during policy activation */
  85         struct list_head                alloc_node;
  86 };
  87
  88 /*
  89  * Policies that need to keep per-blkcg data which is independent
  90  * from any request_queue associated to it must specify its size
  91  * with the cpd_size field of the blkcg_policy structure and
  92  * embed a blkcg_policy_data in it.  cpd_init() is invoked to let
  93  * each policy handle per-blkcg data.
  94  */
  95 struct blkcg_policy_data {
  96         /* the policy id this per-policy data belongs to */
  97         int                             plid;
  98 };
  99
 100 /* association between a blk cgroup and a request queue */
 101 struct blkcg_gq {
 102         /* Pointer to the associated request_queue */
 103         struct request_queue            *q;
 104         struct list_head                q_node;
 105         struct hlist_node               blkcg_node;
 106         struct blkcg                    *blkcg;
 107
 108         /*
 109          * Each blkg gets congested separately and the congestion state is
 110          * propagated to the matching bdi_writeback_congested.
 111          */
 112         struct bdi_writeback_congested  *wb_congested;
 113
 114         /* all non-root blkcg_gq's are guaranteed to have access to parent */
 115         struct blkcg_gq                 *parent;
 116
 117         /* request allocation list for this blkcg-q pair */
 118         struct request_list             rl;
 119
 120         /* reference count */
 121         atomic_t                        refcnt;
 122
 123         /* is this blkg online? protected by both blkcg and q locks */
 124         bool                            online;
 125
 126         struct blkg_policy_data         *pd[BLKCG_MAX_POLS];
 127
 128         struct rcu_head                 rcu_head;
 129 };
 130
 131 typedef void (blkcg_pol_init_cpd_fn)(const struct blkcg *blkcg);
 132 typedef void (blkcg_pol_init_pd_fn)(struct blkcg_gq *blkg);
 133 typedef void (blkcg_pol_online_pd_fn)(struct blkcg_gq *blkg);
 134 typedef void (blkcg_pol_offline_pd_fn)(struct blkcg_gq *blkg);
 135 typedef void (blkcg_pol_exit_pd_fn)(struct blkcg_gq *blkg);
 136 typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);
 137
 138 struct blkcg_policy {
 139         int                             plid;
 140         /* policy specific private data size */
 141         size_t                          pd_size;
 142         /* policy specific per-blkcg data size */
 143         size_t                          cpd_size;
 144         /* cgroup files for the policy */
 145         struct cftype                   *cftypes;
 146
 147         /* operations */
 148         blkcg_pol_init_cpd_fn           *cpd_init_fn;
 149         blkcg_pol_init_pd_fn            *pd_init_fn;
 150         blkcg_pol_online_pd_fn          *pd_online_fn;
 151         blkcg_pol_offline_pd_fn         *pd_offline_fn;
 152         blkcg_pol_exit_pd_fn            *pd_exit_fn;
 153         blkcg_pol_reset_pd_stats_fn     *pd_reset_stats_fn;
 154 };
 155
 156 extern struct blkcg blkcg_root;
 157 extern struct cgroup_subsys_state * const blkcg_root_css;
 158
 159 struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q);
 160 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 161                                     struct request_queue *q);
 162 int blkcg_init_queue(struct request_queue *q);
 163 void blkcg_drain_queue(struct request_queue *q);
 164 void blkcg_exit_queue(struct request_queue *q);
 165
 166 /* Blkio controller policy registration */
 167 int blkcg_policy_register(struct blkcg_policy *pol);
 168 void blkcg_policy_unregister(struct blkcg_policy *pol);
 169 int blkcg_activate_policy(struct request_queue *q,
 170                           const struct blkcg_policy *pol);
 171 void blkcg_deactivate_policy(struct request_queue *q,
 172                              const struct blkcg_policy *pol);
 173
 174 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 175                        u64 (*prfill)(struct seq_file *,
 176                                      struct blkg_policy_data *, int),
 177                        const struct blkcg_policy *pol, int data,
 178                        bool show_total);
 179 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);
 180 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 181                          const struct blkg_rwstat *rwstat);
 182 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off);
 183 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 184                        int off);
 185
 186 u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off);
 187 struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
 188                                              int off);
 189
 190 struct blkg_conf_ctx {
 191         struct gendisk                  *disk;
 192         struct blkcg_gq                 *blkg;
 193         u64                             v;
 194 };
 195
 196 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 197                    const char *input, struct blkg_conf_ctx *ctx);
 198 void blkg_conf_finish(struct blkg_conf_ctx *ctx);
 199
 200
 201 static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 202 {
 203         return css ? container_of(css, struct blkcg, css) : NULL;
 204 }
 205
 206 static inline struct blkcg *task_blkcg(struct task_struct *tsk)
 207 {
 208         return css_to_blkcg(task_css(tsk, blkio_cgrp_id));
 209 }
 210
 211 static inline struct blkcg *bio_blkcg(struct bio *bio)
 212 {
 213         if (bio && bio->bi_css)
 214                 return css_to_blkcg(bio->bi_css);
 215         return task_blkcg(current);
 216 }
 217
 218 static inline struct cgroup_subsys_state *
 219 task_get_blkcg_css(struct task_struct *task)
 220 {
 221         return task_get_css(task, blkio_cgrp_id);
 222 }
 223
 224 /**
 225  * blkcg_parent - get the parent of a blkcg
 226  * @blkcg: blkcg of interest
 227  *
 228  * Return the parent blkcg of @blkcg.  Can be called anytime.
 229  */
 230 static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
 231 {
 232         return css_to_blkcg(blkcg->css.parent);
 233 }
 234
 235 /**
 236  * blkg_to_pdata - get policy private data
 237  * @blkg: blkg of interest
 238  * @pol: policy of interest
 239  *
 240  * Return pointer to private data associated with the @blkg-@pol pair.
 241  */
 242 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 243                                                   struct blkcg_policy *pol)
 244 {
 245         return blkg ? blkg->pd[pol->plid] : NULL;
 246 }
 247
 248 static inline struct blkcg_policy_data *blkcg_to_cpd(struct blkcg *blkcg,
 249                                                      struct blkcg_policy *pol)
 250 {
 251         return blkcg ? blkcg->pd[pol->plid] : NULL;
 252 }
 253
 254 /**
 255  * pdata_to_blkg - get blkg associated with policy private data
 256  * @pd: policy private data of interest
 257  *
 258  * @pd is policy private data.  Determine the blkg it's associated with.
 259  */
 260 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)
 261 {
 262         return pd ? pd->blkg : NULL;
 263 }
 264
 265 /**
 266  * blkg_path - format cgroup path of blkg
 267  * @blkg: blkg of interest
 268  * @buf: target buffer
 269  * @buflen: target buffer length
 270  *
 271  * Format the path of the cgroup of @blkg into @buf.
 272  */
 273 static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
 274 {
 275         char *p;
 276
 277         p = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
 278         if (!p) {
 279                 strncpy(buf, "<unavailable>", buflen);
 280                 return -ENAMETOOLONG;
 281         }
 282
 283         memmove(buf, p, buf + buflen - p);
 284         return 0;
 285 }
 286
 287 /**
 288  * blkg_get - get a blkg reference
 289  * @blkg: blkg to get
 290  *
 291  * The caller should be holding an existing reference.
 292  */
 293 static inline void blkg_get(struct blkcg_gq *blkg)
 294 {
 295         WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
 296         atomic_inc(&blkg->refcnt);
 297 }
 298
 299 void __blkg_release_rcu(struct rcu_head *rcu);
 300
 301 /**
 302  * blkg_put - put a blkg reference
 303  * @blkg: blkg to put
 304  */
 305 static inline void blkg_put(struct blkcg_gq *blkg)
 306 {
 307         WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
 308         if (atomic_dec_and_test(&blkg->refcnt))
 309                 call_rcu(&blkg->rcu_head, __blkg_release_rcu);
 310 }
 311
 312 struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
 313                                bool update_hint);
 314
 315 /**
 316  * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
 317  * @d_blkg: loop cursor pointing to the current descendant
 318  * @pos_css: used for iteration
 319  * @p_blkg: target blkg to walk descendants of
 320  *
 321  * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
 322  * read locked.  If called under either blkcg or queue lock, the iteration
 323  * is guaranteed to include all and only online blkgs.  The caller may
 324  * update @pos_css by calling css_rightmost_descendant() to skip subtree.
 325  * @p_blkg is included in the iteration and the first node to be visited.
 326  */
 327 #define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)           \
 328         css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)   \
 329                 if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),    \
 330                                               (p_blkg)->q, false)))
 331
 332 /**
 333  * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
 334  * @d_blkg: loop cursor pointing to the current descendant
 335  * @pos_css: used for iteration
 336  * @p_blkg: target blkg to walk descendants of
 337  *
 338  * Similar to blkg_for_each_descendant_pre() but performs post-order
 339  * traversal instead.  Synchronization rules are the same.  @p_blkg is
 340  * included in the iteration and the last node to be visited.
 341  */
 342 #define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)          \
 343         css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)  \
 344                 if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),    \
 345                                               (p_blkg)->q, false)))
 346
 347 /**
 348  * blk_get_rl - get request_list to use
 349  * @q: request_queue of interest
 350  * @bio: bio which will be attached to the allocated request (may be %NULL)
 351  *
 352  * The caller wants to allocate a request from @q to use for @bio.  Find
 353  * the request_list to use and obtain a reference on it.  Should be called
 354  * under queue_lock.  This function is guaranteed to return non-%NULL
 355  * request_list.
 356  */
 357 static inline struct request_list *blk_get_rl(struct request_queue *q,
 358                                               struct bio *bio)
 359 {
 360         struct blkcg *blkcg;
 361         struct blkcg_gq *blkg;
 362
 363         rcu_read_lock();
 364
 365         blkcg = bio_blkcg(bio);
 366
 367         /* bypass blkg lookup and use @q->root_rl directly for root */
 368         if (blkcg == &blkcg_root)
 369                 goto root_rl;
 370
 371         /*
 372          * Try to use blkg->rl.  blkg lookup may fail under memory pressure
 373          * or if either the blkcg or queue is going away.  Fall back to
 374          * root_rl in such cases.
 375          */
 376         blkg = blkg_lookup_create(blkcg, q);
 377         if (unlikely(IS_ERR(blkg)))
 378                 goto root_rl;
 379
 380         blkg_get(blkg);
 381         rcu_read_unlock();
 382         return &blkg->rl;
 383 root_rl:
 384         rcu_read_unlock();
 385         return &q->root_rl;
 386 }
 387
 388 /**
 389  * blk_put_rl - put request_list
 390  * @rl: request_list to put
 391  *
 392  * Put the reference acquired by blk_get_rl().  Should be called under
 393  * queue_lock.
 394  */
 395 static inline void blk_put_rl(struct request_list *rl)
 396 {
 397         /* root_rl may not have blkg set */
 398         if (rl->blkg && rl->blkg->blkcg != &blkcg_root)
 399                 blkg_put(rl->blkg);
 400 }
 401
 402 /**
 403  * blk_rq_set_rl - associate a request with a request_list
 404  * @rq: request of interest
 405  * @rl: target request_list
 406  *
 407  * Associate @rq with @rl so that accounting and freeing can know the
 408  * request_list @rq came from.
 409  */
 410 static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
 411 {
 412         rq->rl = rl;
 413 }
 414
 415 /**
 416  * blk_rq_rl - return the request_list a request came from
 417  * @rq: request of interest
 418  *
 419  * Return the request_list @rq is allocated from.
 420  */
 421 static inline struct request_list *blk_rq_rl(struct request *rq)
 422 {
 423         return rq->rl;
 424 }
 425
 426 struct request_list *__blk_queue_next_rl(struct request_list *rl,
 427                                          struct request_queue *q);
 428 /**
 429  * blk_queue_for_each_rl - iterate through all request_lists of a request_queue
 430  *
 431  * Should be used under queue_lock.
 432  */
 433 #define blk_queue_for_each_rl(rl, q)    \
 434         for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))
 435
 436 static inline void blkg_stat_init(struct blkg_stat *stat)
 437 {
 438         u64_stats_init(&stat->syncp);
 439 }
 440
 441 /**
 442  * blkg_stat_add - add a value to a blkg_stat
 443  * @stat: target blkg_stat
 444  * @val: value to add
 445  *
 446  * Add @val to @stat.  The caller is responsible for synchronizing calls to
 447  * this function.
 448  */
 449 static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
 450 {
 451         u64_stats_update_begin(&stat->syncp);
 452         stat->cnt += val;
 453         u64_stats_update_end(&stat->syncp);
 454 }
 455
 456 /**
 457  * blkg_stat_read - read the current value of a blkg_stat
 458  * @stat: blkg_stat to read
 459  *
 460  * Read the current value of @stat.  This function can be called without
 461  * synchroniztion and takes care of u64 atomicity.
 462  */
 463 static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
 464 {
 465         unsigned int start;
 466         uint64_t v;
 467
 468         do {
 469                 start = u64_stats_fetch_begin_irq(&stat->syncp);
 470                 v = stat->cnt;
 471         } while (u64_stats_fetch_retry_irq(&stat->syncp, start));
 472
 473         return v;
 474 }
 475
 476 /**
 477  * blkg_stat_reset - reset a blkg_stat
 478  * @stat: blkg_stat to reset
 479  */
 480 static inline void blkg_stat_reset(struct blkg_stat *stat)
 481 {
 482         stat->cnt = 0;
 483 }
 484
 485 /**
 486  * blkg_stat_merge - merge a blkg_stat into another
 487  * @to: the destination blkg_stat
 488  * @from: the source
 489  *
 490  * Add @from's count to @to.
 491  */
 492 static inline void blkg_stat_merge(struct blkg_stat *to, struct blkg_stat *from)
 493 {
 494         blkg_stat_add(to, blkg_stat_read(from));
 495 }
 496
 497 static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)
 498 {
 499         u64_stats_init(&rwstat->syncp);
 500 }
 501
 502 /**
 503  * blkg_rwstat_add - add a value to a blkg_rwstat
 504  * @rwstat: target blkg_rwstat
 505  * @rw: mask of REQ_{WRITE|SYNC}
 506  * @val: value to add
 507  *
 508  * Add @val to @rwstat.  The counters are chosen according to @rw.  The
 509  * caller is responsible for synchronizing calls to this function.
 510  */
 511 static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
 512                                    int rw, uint64_t val)
 513 {
 514         u64_stats_update_begin(&rwstat->syncp);
 515
 516         if (rw & REQ_WRITE)
 517                 rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
 518         else
 519                 rwstat->cnt[BLKG_RWSTAT_READ] += val;
 520         if (rw & REQ_SYNC)
 521                 rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
 522         else
 523                 rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
 524
 525         u64_stats_update_end(&rwstat->syncp);
 526 }
 527
 528 /**
 529  * blkg_rwstat_read - read the current values of a blkg_rwstat
 530  * @rwstat: blkg_rwstat to read
 531  *
 532  * Read the current snapshot of @rwstat and return it as the return value.
 533  * This function can be called without synchronization and takes care of
 534  * u64 atomicity.
 535  */
 536 static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
 537 {
 538         unsigned int start;
 539         struct blkg_rwstat tmp;
 540
 541         do {
 542                 start = u64_stats_fetch_begin_irq(&rwstat->syncp);
 543                 tmp = *rwstat;
 544         } while (u64_stats_fetch_retry_irq(&rwstat->syncp, start));
 545
 546         return tmp;
 547 }
 548
 549 /**
 550  * blkg_rwstat_total - read the total count of a blkg_rwstat
 551  * @rwstat: blkg_rwstat to read
 552  *
 553  * Return the total count of @rwstat regardless of the IO direction.  This
 554  * function can be called without synchronization and takes care of u64
 555  * atomicity.
 556  */
 557 static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)
 558 {
 559         struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
 560
 561         return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
 562 }
 563
 564 /**
 565  * blkg_rwstat_reset - reset a blkg_rwstat
 566  * @rwstat: blkg_rwstat to reset
 567  */
 568 static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
 569 {
 570         memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
 571 }
 572
 573 /**
 574  * blkg_rwstat_merge - merge a blkg_rwstat into another
 575  * @to: the destination blkg_rwstat
 576  * @from: the source
 577  *
 578  * Add @from's counts to @to.
 579  */
 580 static inline void blkg_rwstat_merge(struct blkg_rwstat *to,
 581                                      struct blkg_rwstat *from)
 582 {
 583         struct blkg_rwstat v = blkg_rwstat_read(from);
 584         int i;
 585
 586         u64_stats_update_begin(&to->syncp);
 587         for (i = 0; i < BLKG_RWSTAT_NR; i++)
 588                 to->cnt[i] += v.cnt[i];
 589         u64_stats_update_end(&to->syncp);
 590 }
 591
 592 #else   /* CONFIG_BLK_CGROUP */
 593
 594 struct blkcg {
 595 };
 596
 597 struct blkg_policy_data {
 598 };
 599
 600 struct blkcg_policy_data {
 601 };
 602
 603 struct blkcg_gq {
 604 };
 605
 606 struct blkcg_policy {
 607 };
 608
 609 #define blkcg_root_css  ((struct cgroup_subsys_state *)ERR_PTR(-EINVAL))
 610
 611 static inline struct cgroup_subsys_state *
 612 task_get_blkcg_css(struct task_struct *task)
 613 {
 614         return NULL;
 615 }
 616
 617 #ifdef CONFIG_BLOCK
 618
 619 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
 620 static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
 621 static inline void blkcg_drain_queue(struct request_queue *q) { }
 622 static inline void blkcg_exit_queue(struct request_queue *q) { }
 623 static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
 624 static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }
 625 static inline int blkcg_activate_policy(struct request_queue *q,
 626                                         const struct blkcg_policy *pol) { return 0; }
 627 static inline void blkcg_deactivate_policy(struct request_queue *q,
 628                                            const struct blkcg_policy *pol) { }
 629
 630 static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
 631
 632 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 633                                                   struct blkcg_policy *pol) { return NULL; }
 634 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
 635 static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
 636 static inline void blkg_get(struct blkcg_gq *blkg) { }
 637 static inline void blkg_put(struct blkcg_gq *blkg) { }
 638
 639 static inline struct request_list *blk_get_rl(struct request_queue *q,
 640                                               struct bio *bio) { return &q->root_rl; }
 641 static inline void blk_put_rl(struct request_list *rl) { }
 642 static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl) { }
 643 static inline struct request_list *blk_rq_rl(struct request *rq) { return &rq->q->root_rl; }
 644
 645 #define blk_queue_for_each_rl(rl, q)    \
 646         for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
 647
 648 #endif  /* CONFIG_BLOCK */
 649 #endif  /* CONFIG_BLK_CGROUP */
 650 #endif  /* _BLK_CGROUP_H */